This invention relates to air gun which are used to deliver a stream of pressurized air to a work area. More particularly, this invention relates to safety air guns which have a dead end pressure of less than thirty pounds per square inch (psi).
Compressed air is widely used in industry to power pneumatic tools such as air hammers, nail guns, and pneumatic wrenches. The line pressure needed to operate such tools is typically between 85 and 125 psi. Workers have found that compressed air from such lines can be effective for dusting and for the removal of debris from a work area. Accordingly, air guns are routinely interchanged with pneumatic tools when the work area needs cleaning.
Pressurized air can be very dangerous in the work place. In the past, either by accident or as a result of a practical Joke, workmen have been subjected to the high pressure air stream. If this air stream comes in close contact with exposed skin, it may penetrate the epidermis and enter the blood stream. Air bubbles may then proceed to the brain causing immediate death.
In response to concerns over worker safety, the Occupational Safety and Health Administration (OSHA) has promulgated Rule 1910.242(b). The Rule states that compressed air used for cleaning must not exceed thirty psi. This is a measurement of "dead end" pressure with no air escaping from the gun's outlet nozzle. Additionally, the Rule states that air pressure cleaning can only be used with effective chip guarding and personal protection equipment.
Various air gun designs have attempted to solve this problem. Frequently, escape holes are provided in the side of an air outlet tube to release air if the outlet opening is blocked. In some guns air is drawn into the outlet tube through the side openings when the outlet opening is not blocked. While these designs have adequately reduced the dead end (blocked outlet) output pressure to a safe level, they are easily modified by a worker to produce a more powerful tool. A worker can simply wrap tape around the escape holes to block air passage therethrough. The result is a tool with a more powerful air stream. However, the tool is now more dangerous since the dead end pressure is now equal to the line pressure of 85 to 125 psi.
It is an object of the present invention to provide a safety air gun which effectively reduces line pressure of 85 to 125 psi to a safe level below thirty psi, while providing a tamper resistant design that severely reduces the incentive for worker modification. Another object of the invention is to provide a tamper resistant safety air gun that conserves pressurizing air by drawing ambient air into the air stream through the gun.